Sensor connection means

ABSTRACT

The invention relates to a sensor adapted for electrical connection to a power source having an electrical contact means ( 3 ). The sensor has a first insulating substrate ( 1 ) carrying a first electrode ( 2 ) and a second insulating substrate ( 7 ) carrying a second electrode ( 6 ). The electrodes are disposed to face each other in spaced apart relationship, sandwiching a spacer ( 4 ) therebetween. A first cut-out portion extends through the first insulating substrate ( 1 ) and a spacer ( 4 ) to expose a first contact area ( 23 ) on the second insulating substrate ( 7 ). This permits the electrical contact means ( 31 ) to effect electrical connection with the first contact ( 23 ) which in turn is in electrically conductive connection with the second electrode ( 6 ). A similar contact arrangement may be disposed on the opposite side of the sensor.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/399,512, filed 20 Sep. 1999, now U.S. Pat. No. 6,379,513, which is acontinuation of PCT International application No. PCT/AU98/00184 whichhas an International filing date of Mar. 20, 1998, which designated theUnited States of America, and which was published by the InternationalBureau in English on Oct. 1, 1998.

TECHNICAL FIELD

This invention relates to disposable electrochemical sensors of the typeused for quantitative analysis, for example, of glucose levels in blood,for pH measurement, or the like. More particularly the invention relatesto means for electrical connection of such sensors to a measuringapparatus.

BACKGROUND ART

U.S. Pat. No. 5,437,999 discloses an electrochemical sensor of the kindwhich in use is electrically connected with a power source. The sensoris constructed from two spaced apart printed circuit boards each havinga metal layer on one side and disposed so that the metal layers arefacing each other in spaced apart relationship. The metal layers arephotolithographically treated to define electrode areas which form partof a cell. At one end of the assembly the electrode substrates are cutto provide laterally spaced protruding tabs bearing the metal layer. Theexposed metal surfaces of the tabs act as contact pads, each contact padbeing electrically connected with a corresponding electrode. The contactpads in turn engage contact prongs connected to a power source andprovide electrical connection between the sensor and a power source.

The arrangement of U.S. Pat. No. 5,437,999 suffers from thedisadvantages that the substrate is required to be of considerablerigidity in order to ensure satisfactory and reliable electricalcontact. Moreover the user is often left uncertain as to whether asensor has satisfactorily been connected with the power source.

In co-pending applications PCT/AU96/00207, PCT/AU96/00365,PCT/AU96/00723 and PCT/AU96/00724 there are described various very thinelectrochemical cells. Each cell is defined between facing spaced apartelectrodes which are formed as thin metal coatings (for example sputtercoatings) deposited on thin inert plastic film (for example 100 micronthick PET). The electrodes are separated one from the other by a spacerof thickness of for example 500 μm or less.

The connection arrangement of U.S. Pat. No. 5,437,999 is not suitablefor use with the extremely thin sensor devices of the kind discussed inour co-pending applications in view of the flexibility of the insulatingelectrode carriers. In general, it is desirable that the disposablesensor be capable of simple, quick, reliable and effective connectionwith the power source in the measuring device by unskilled users. It isan object of the present invention to overcome or ameliorate at leastone of the disadvantages of the prior art, or to provide a usefulalternative.

DESCRIPTION OF THE INVENTION

According to a first aspect, the invention provides a sensor adapted forelectrical connection with a power source having first contact means,the sensor comprising:

a first insulating substrate carrying a first electrode and a secondinsulating substrate carrying a second electrode, said electrodes beingdisposed to face each other in spaced apart relationship,

a first cut-out portion extending through said first insulatingsubstrate and a spacer to expose a first contact area on the secondinsulating substrate to permit a first contact means to effectelectrical connection with the first contact area disposed on the secondinsulating substrate, the first contact area being in electricallyconductive connection with the second electrode.

The first contact area may be maintained at a predetermined depth fromthe first insulating substrate.

According to a second aspect, the invention provides a sensor accordingto the first aspect further comprising a second cut-out portionextending through said second insulating substrate and the, or another,spacer to expose a second contact area on the first insulating substrateto permit a second contact means to effect electrical connection with asecond contact area disposed on the first insulating substrate, thesecond contact area being in electrically conductive connection with thefirst electrode.

The second contact area may be maintained at a predetermined depth fromthe second insulating substrate.

According to a third aspect, the invention also provides a sensingsystem comprising a sensor according to the first or second aspects anda sensing apparatus including a first contact means and/or secondcontact means adapted to effect electrical contact with the first andsecond contact areas respectively.

“Comprising” as herein used is used in an inclusive sense, that is tosay in the sense of “including” or “containing.” The term is notintended in an exclusive sense (“consisting of” or “composed of”).

In preferred embodiments the insulating substrate is made of a flexibleinsulating material. The second electrode and the first contact area areformed from a unified layer of metal deposited on the first substrate,and more preferably deposited by being sputter coated thereon. Suitablemetals include, but are not limited to palladium, gold, platinum,iridium, and silver. Carbon may also be used. Desirably the contactor isa metal contactor which is resiliently biased to extend through thefirst cut-out portion to make contact with the metal first contact areaon the second substrate. In highly preferred embodiments the contactoris adapted for click engagement with the cut-out portion which extendsthrough the first insulating substrate and the spacer.

With a connector according to the current invention the spacer layerprovides extra strength. A rigid connector can therefore be formed usingflexible materials. This allows a wider range of materials to beutilized. An audible confirmation of connection can also be simplyprovided by the current invention unlike the connector described in U.S.Pat. No. 5,437,999.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only withreference to the accompanying drawings in which:

FIG. 1 shows a first embodiment of a sensor according to the inventionin plan view.

FIG. 2 shows a scrap side elevation of the sensor of FIG. 1 incross-section on line 10—10.

FIG. 3 is a diagrammatic enlargement showing a part of the sensor ofFIG. 2 in engagement with contacts.

FIG. 4 shows an end elevation of the sensor of FIG. 3 in section on lineA—A.

FIG. 5 shows a second embodiment of the invention in plan view.

FIG. 6 shows a cross-section of the embodiment of FIG. 5 in endelevation when viewed on line C—C.

FIG. 7 shows a cross-section of the embodiment of FIG. 5 in sideelevation on line D—D.

FIG. 8 shows a third embodiment of the invention in plan view.

BEST MODES FOR CARRYING OUT THE INVENTION

With reference to FIGS. 1 to 3 there is shown a first embodiment of anelectrochemical sensor. The sensor comprises a polyester spacer 4approximately 25 mm×5 mm and 100 microns thick and having a circularaperture 8 of 3.4 mm diameter. Aperture 8 defines a cylindrical cellwall 10. Adhered to one side of spacer 4 is a first insulating substratepolyester sheet 1 having a first coating of palladium 2. The palladiumwas sputter coated on sheet 1 at between 4 and 5 millibar pressure in anatmosphere of argon gas to give a uniform coating thickness of about100–1000 angstroms. Sheet 1 is adhered by means of adhesive 3 to spacer4 with palladium coating 2 adjacent spacer 4 and covering one side ofaperture 8.

A second insulating substrate 7 consists of a polyester sheet having asecond sputter coating 6 of palladium adhered by means of contactadhesive 5 to the other side of spacer 4 and covering the opposite sideof aperture 8. There is thereby defined a cell having cylindrical sidewall 10 and closed at one cylinder end by a first electrode of palladiummetal 2. The other cylinder end wall is a second electrode formed frompalladium 6. The assembly is notched at 9 to provide a means foradmission of a solution to the cell, and to allow air to escape.

Adjacent one end 20 a cut-out aperture 21 pierces first insulating layer1 and first metal layer 2. In the present example cut-out 21 isoval-shaped. A corresponding cut-out portion 22 in spacer 4 is inregistration with cut-out 21. FIG. 3 shows a side elevationcross-section of sensor 1 inserted into a receiving slot formed in part30 of measuring apparatus and to which is mounted a first resilientcontactor 31 and a second resilient contactor 32. Upon insertion ofsensor end 20 into the slot, contactor 31 rides over the outer surfaceof insulating layer 1 and clicks into the well formed by apertures 21and 22 to engage a first contact area portion 23 of metal layer 6. Firstcontact area 23 is a portion of the same metal layer 6 deposited oninsulating layer 7 from which the second electrode is formed and istherefore in electrically conductive communication with the secondelectrode area of cell 8. Contact area 23 is in effect defined by thediameter of cut-out 20 of spacer 4 in the present example.

In the embodiment shown in FIG. 1 a second circular cut-out portion 25spaced further from edge 20 than aperture 21 extends through secondinsulating layer 7 and second metal layer 6. A cut-out portion 26 (seeFIG. 2) of spacer 4 corresponds with an registers with cut-out portion25 of insulating layer 7. Referring again to FIG. 3, in use the sensoris configured to permit a second resiliently biased contactor 32 toextend through the well defined by cut-out portions 25 and 26 wherebyresilient contactor 32 engages and makes electrical contact with metallayer 2 at 27 and thereby with the first electrode 2 of cell 8.

Resilient connectors 31 and 32 are arranged in a slot 30 of themeasuring device and are electrically connected in a measuring circuit.In use, the sensor is inserted into slot 30 with edge 20 leading. Thefirst resilient contactor 31 rides over the end margin of the sensor 1until it encounters first aperture 21, 22 whereupon it click engageswith the opening and makes electrical contact with the first contactarea 23 of metal layer 6. Slight additional insertion of sensor 1 inslot 30 causes the second contactor 32 to click engage with the secondaperture 25, 26 and make contact with second contact area 27 of metallayer 2.

Spacer 4 surrounds both apertures and ensures that, despite theintrinsic flexibility of the insulating layers and the thinness of thesensor, electrical contact can be made with reliable precision.

A second embodiment of the invention is shown in FIGS. 5, 6 and 7wherein parts corresponding in function to corresponding parts of theembodiment of FIGS. 1 and 2 are identified by corresponding numerals.The major difference between the second embodiment and the first is thatin the second embodiment cut-out portions 21, 22 are cut from one sideedge of sensor 1 while cut-out portions 25, 26 are cut out from theopposite side edge of the sensor 1. In this case contactors 31 and 32are spaced laterally and click substantially simultaneously into theirrespective cut-out opening. The cut-out openings are surrounded on threesides by spacer 4, the fourth side being exposed at respective edges ofthe sensor.

Although in the embodiment shown in FIGS. 5, 6 and 7 the openings are ata corresponding distance from end 20 in other embodiments they could bespaced in the longitudinal direction as is the case in the firstdescribed embodiment. This ensures that contact is only made when thesensor is inserted in a correct orientation and ensures correctpolarity.

A third embodiment is shown schematically in FIG. 8. In this case theopenings take the form of slots 21, 25 extending longitudinally fromedge 20. For preference spacer 4 extends around all edges of openings 21and 25 of FIG. 8 but in a less preferred embodiment spacer 4 onlyextends on three sides of slots 21 and 25 in which case click engagementis not obtained or is obtained only if the contacts extend from theopposite direction. However, the advantage that the contact pad area ofthe sensor is at a predetermined dimension from the opposite face ismaintained. If desired the slots can differ in length and co-operationwith contacts spaced longitudinally so that contact with both contactsrequires correctly orientated insertion of the sensor.

It will be understood that both construction materials and dimensionsare given merely by way of example and that sensors of a differingdesign or construction may utilize the invention. One, two or more thantwo contacts may be provided by the means shown. The invention extendsto include a power source or measuring device when connected to a sensorby the means described. Any suitable form of contactor may be used withsensors according to the invention.

1. A sensor adapted for electrical connection with a power source havinga contactor, the sensor comprising: a first insulating substratecarrying a first electrode and a second insulating substrate carrying asecond electrode, said electrodes being disposed to face each other inspaced apart relationship, a spacer positioned between the first andsecond insulating substrates and having an aperture defining a wall of acell, the cell closed at either end by the first and second electrodes,a first cut-out portion extending through said first insulatingsubstrate and the spacer to expose a first contact area on the secondinsulating substrate to permit the contactor to effect electricalconnection with the first contact area disposed on the second insulatingsubstrate, the first contact area being in electrically conductiveconnection with the second electrode.
 2. A sensor according to claim 1wherein the first contact area is maintained at a predetermined depthfrom the first insulating substrate.
 3. A sensor according to claim 1wherein each insulating substrate is made of a flexible insulatingmaterial.
 4. A sensor according to claim 3 wherein the flexibleinsulating material is polyester.
 5. A sensor according to claim 1wherein each electrode and its respective contact area are formed from alayer of metal deposited on the insulating substrate.
 6. A sensoraccording to claim 5 wherein the metal is selected from the groupconsisting of palladium, gold, platinum, iridium and silver.
 7. A sensoraccording to claim 5 wherein the metal is 10–1000 nanometers thick.
 8. Asensor according to claim 5 wherein the layer of metal is deposited onthe substrate by sputter coating.
 9. A sensor according to claim 1wherein each electrode and the first contact area are formed fromcarbon.
 10. A sensor according to claim 1 wherein a second cut-outportion extends through said second insulating substrate and a spacer toexpose the second contact area on the first insulating substrate, thefirst and second cut-out portions being laterally spaced apart relativeto the longitudinal axis of the sensor.
 11. A sensor according to claim1 wherein a second cut-out portion extends through said secondinsulating substrate and a spacer to expose the second contact area onthe first insulating substrate, the first and second cut-out portionsbeing longitudinally spaced relative to the longitudinal axis of thesensor.
 12. A sensor according to claim 1 wherein a second cut-outportion extends through said second insulating substrate and a spacer toexpose the second contact area on the first insulating substrate, thefirst and second cut-out portions being laterally and longitudinallyspaced relative to the longitudinal axis of the sensor.
 13. A sensoraccording to claim 1 wherein at least one of the substrate or spacerextends around the entire periphery of the cut-out portion.
 14. A sensoraccording to claim 1 wherein the cut-out portion is adapted for clickengagement with a contactor.
 15. A sensor according to claim 1 whereinthe cut-out portion is cut from an edge of the sensor such that thecut-out portion is open on at least one edge of the sensor.
 16. Asensing system comprising a sensor according to claim 1, and a sensingapparatus comprising a first contactor adapted to effect electricalcontact with the first contact area.
 17. A sensing system according toclaim 16, further comprising a second contactor adapted to effectelectrical contact with a second contact area, wherein a second cut-outportion extends through said second insulating substrate and a spacer toexpose the second contact area on the first insulating substrate.
 18. Asensing system according to claim 17 wherein the second contactor isresiliently biased to extend through the second cut-out portion to makecontact with the second contact area.
 19. A sensing system according toclaim 17 wherein the second contactor is adapted for click engagementwith the second cut-out portion.
 20. A sensing system according to claim16 wherein the first contactor is resiliently biased to extend throughthe first cut-out portion to make contact with the first contact area.21. A sensing system according to claim 16 wherein the first contactoris adapted for click engagement with the first cut-out portion.
 22. Asensor adapted for electrical connection with a power source having acontactor, the sensor comprising: a first insulating substrate carryinga first electrode and a second insulating substrate carrying a secondelectrode, said electrodes being disposed to face each other in spacedapart relationship, a first cut-out portion extending through said firstinsulating substrate and a spacer to expose a first contact area on thesecond insulating substrate to permit the contactor to effect electricalconnection with the first contact area disposed on the second insulatingsubstrate, the first contact area being in electrically conductiveconnection with the second electrode, and a second cut-out portionextending through said second insulating substrate and the spacer toexpose a second contact area on the first insulating substrate, thefirst and second cut-out portions being longitudinally spaced relativeto the longitudinal axis of the sensor.
 23. A sensor adapted forelectrical connection with a power source having a contactor, the sensorcomprising: a first insulating substrate carrying a first electrode anda second insulating substrate carrying a second electrode, saidelectrodes being disposed to face each other in spaced apartrelationship; a first cut-out portion extending through said firstinsulating substrate and a spacer to expose a first contact area on thesecond insulating substrate to permit the contactor to effect electricalconnection with the first contact area disposed on the second insulatingsubstrate, the first contact area being in electrically conductiveconnection with the second electrode; and a second cut-out portionextending through said second insulating substrate and the spacer toexpose a second contact area on the first insulating substrate, thefirst and second cut-out portions being laterally and longitudinallyspaced relative to the longitudinal axis of the sensor.